Coated iron or steel article and method of making the same



Patented Aug. 23, 1932 UNITED STATES PATENT? OFFICE ROBERT E. TANNER, OF DE!!!IBOIl'IZ, MICHIGAN, ASSIGNOR TO PABKEB BUST-PROOF COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN comm) mom or. s'rnnn narrate m un'rnonor manna 'rnn em No ,Drawing.

This invention relates to a coated article of iron or steel and a method of making the same. The object of the invention is to produce an article having a rust-resisting coat-- ing of desired appearance and reslstant to heat, and to produce such an article in an economical and efficient manner. More particularly, the object isto produce an article of iron or steel or having a surface of iron or steel, the surface being covered with a coating consisting of substantially insoluble phosphates and cupric oxide. Further details of the objects of the invention and the manner of carryin it out will appear as the description procee s.

The method of rust-proofing iron or steel surfaces by forming thereon substantially insoluble phosphates is well known. Thecustomary practice has been to form a dilute solution of soluble phosphates and phosphoric acid and boil the iron or steel articles therein until the desired coating forms on their surfaces. A patent to Green et al, No. 1,651,694 of December 6, 1927, may bereferred to as specifying one particular composition and method of'making and using the same which has been commercially successful. It will be understood, however, that the present invention applies to other methods of producing ,a dilute phosphate bath which will form the desired coating on articles of iron or steel.

It has been found that the addition of copper to the dilute solution of phosphates renders the action of the solution much more rapid and, for that reason, more economical. This is brou ht out fully and with considerable particu larity in my joint application with Darsey, Serial No. 331,705, filed January 10, 1929. When the solution is produced so that it contains, in addition to the phosphate of iron and of metals more basic than iron, a small percentage of phosphate of copper, there is deposited upon the surface of iron or steel a coating of substantially,

insoluble phosphates of iron and of the metal more basic than iron interspersed with minute particles of metallic cop er. The copper may be present also to a slig t extent in combination, but the larger portion of it appears to be in the metallic state.

Application filed. April 22, 1929. Serial No. 357,343.

- A coating of insoluble phosphates and metallic copper has been found to form a very good base for paint, varnish, enamel, or the like, but if left uncovered, is not as rust-resistant as the coating of insoluble phosphates without the presence of thecopper. ably this is because each particle of copper tends'to formwith the adjacent iron or steel, a galvanic couple, which facilitates rusting action. v p

According to the present invention, a coating is produced on articles of iron or steel in the manner indicated above, so that it is composed of insoluble phosphates interspersed with metallic copper. The copper is then oxidized. This may be done by heating the surfaces to be treated over an oxidizing flame to approximate red heat. The copper particles are first oxidized to cuprous oxide, which stage may be noted by the rust color produced, and thereafter the red oxide of copper is further oxidized to cupric oxide, resulting in a black color.

A coating such as described and containing metallic copper is not of a color generally pleasing and the coating thus blackthe ordinary manner without the presence,

of copper in the solution. Cuprous oxide is preferable to cupric oxide for heat resistance, and is as satisfactory otherwise except as to color.

For most purposes, a coating is preferable that contains no more copper than is deposited by a solution containing as an approximate maximum one-tenth as much copper dissolved in the solution as there is iron or other metal more'basic than iron dissolved in the solution. However, a somewhat larger proportion of copper is permissible and benecial for heat resisting urposes. 1

While the oxidation 0 the copper has been Probdescribed as being the result of exposing it to an oxidizing flame until heated to approximately red heat, it will be readily understood that other practicable methods of oxidation may be employed with the same result. Other variations from the specific features described above may be made within I the scope of the appended claims.

What I claim is:

1.An article of iron or steel or having a surface of iron or steel, coated with insoluble phosphates interspersed with oxide of copper.

2. An article of iron or steel or having a surface of iron on'steel, coated with insoluble phosphates interspersed with cupric oxide.

3. A method of coating surfaces of iron' or steel which comprises applying to said surfaces a hot weak dilute solution of phosphates including copper phosphate, the cop-- per phosphate forming only a minor fraction of the phosphates in solution, and thereby forming on the said surfaces a coating of insoluble phosphates interspersed with metallic copper, and heating to oxidize the copper in said coating.

' 4. A method of coating surfaces of iron or steel which comprises applying .to said surfaces a hot weak dilute solution of phosphates including copper phosphate, the .copper phosphate forming only a minor fraction of the phosphatesin solution, and thereby forming on the said surfaces a coating of insoluble phosphates interspersed with metallic copper, and heating to oxidize the copper in said coating to cupric oxide.

5. A method of coating surfaces of iron or steel which'comprises applying to said surfaces a hot weak dilute solutionof phosphates including copper phosphate, the copper phosphate forming only a minor fraction of tie phosphates in solution, and thereby forming on the said surfaces a coating of insoluble phosphates interspersed with metal copper, and subjecting the coating to an oxidizing flame and thereby oxidizing the metallic copper in the coating.

6. The method of treating a coating of insoluble phosphates interspersed with metallic copperwhich consists in heating in an oxidizing atmosphere until the metallic copper in the coating is oxidized.

In testimony whereof I have hereunto signed my name to this specification.

ROBERT R. TANNER. 

